Insulating bushing



Patented Apr. 6, 1943 2,315,623 INSULATING BUSHING William HLJacobl, Wilkinsburg, Pa., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa, a-corporation ol' Pennsylvania Application April 11, 1941, Serial No. 388,089

a Claims. (Cl. 174- 19) T of the bushing to The present invention relates to bushings for insulating the conducting leads. of high tension electrical apparatus such as transformers and circuit breakers and it has particular relation to therebetween. v

Aiurther object of the invention is to provide an insulating bushing, the ends and other openan improved means for-sealing the interior ings of which are efifectively sealed by means of such a bushing from the outside air and molsresilient sleeve members. t y a fother objects and advantages of the inven- Bushings of this type generally comprise an tion will appear from the following detailed deelongated tubular casing of insulating material] scription readin conjunction with the accornsuch as porcelain, through which the conductor panying drawing in which: l or lead iromthe apparatus extends to be con- Figure 1 is a view e at o with parts nccted at the upper end of the casing to an outbroken away, of a bushlngassembly in accordside terminal. This terminal is in turn adapted ance W the Present invention, i to be connected to an electric supply circuit. By i 2 is an en arged vertical view; w t pa s reason of the diiference in the temperaturecoin section a d pa s broken warm! e p a aefllcients of expansion of the insulating casing we of Fig. 1. and the metallic conductonit is diillcult to main- Fig. 3 is an enlarged sectional view of the re- 1 tain the bushing fluid-tight and to prevent movable plug shown in Fig. 2, and breathing of the outside atmosphere upon st 4 s a view s mila to Fla- 2 o a po t on changes in temperature. The bushings are usuof a modification 1' e invention. a I ally fllled'wlth a dielectric fluid, such as a gum Re e in to F i e ra he bush- 7 or oil, from which all impurities must be exs ay compr s il c s 2 of dielect ic elud d, I I material, such as porcelain, having a plurality 01' With the prior art methods of sealing the I surface creepage nges 4 of a usualjconstruce inside of the bushing, the insulating casing is tion. The casing 2 rests p t lic S eeve generally compressed between parts fixed to the 6 which supports a metallic clamping fl e 8. I metallicconductor and as a result may be sub- The flange 8 is secured to the casing ill of an jected to severe stresses upon changes of tem electr transformer 1 Similar pp tus by perature. According to the present invention, means of bo s I however, a weatherproof seal is provided withso By way of exampl the p e en inv n y cut subjecting the insulating casing to such danbe used with a bushing of the condenser type in gerous stresses. This is accomplished by prowhich elongated layers of conducting and 511- viding a resilient sleeve member between the conlating material a e Wou d ml d 1 8 meta i ductor and the opening in the insulating casing. conductor: In the drawing, the condenser wrap- This sleeve is adapted to close the space between ping which is designated as H is applied to a these two members irrespective of relative longlterminal stud or conductor Ii. The central portudinal movement therebetween and will-protion of this condenser is disposed within the 'mevide asatisiactory seal without exerting any par- I tailic collar. or sleeve 6 which may be applied ticular force on the casing. It is within the scope thereto in any suitable manner such as that of the invention to vulcanize or cement this reshown in Patent No. 2,088,502, issued July 27, silient sleeve to either one or both of the meme 1937, to E. E. Arnold et a1. It is intended that bars which it contacts in order to maintain 'it the condenser wrapping fit tightly within the in place; This latter result may also be accomcollar so that an oil-tight Joint is obtainedthereplished by means of collar members secured to between to prevent leakage of insulating fluid. the conductor in lieu of vulcanizing or cement- Referringto Fig. 2, it will be seen that ,the a I I lower end of the tubular casing 4 is provided with I It is accordingly an object of the present inven-- an opening indicated at II. This opening is tion to provide a bushing construction which is nearly Cy n but P r y tapers slightly comparatively simple and which provides a comto an increased diameter at its outer end. The pletely weatherproof seal without causing any "conductor and condenser structure is disposed dangerous stresses to be exerted upon the in-, within the bushing in such a manner that the sulating casing. metallic sleeve 6 fits within the opening I! and a It is another object of the invention toprovide resilient sleeve member 20 is disposed within the I an insulating bushing in which a resilient sleeve annular space therebetween to close the bottom is disposed between the conductor and the end of the bushing about the'metallic sleeve. It is iurnisha moisture-proof seal when the vulcanizing or cementing is dispensed with.

A metallic collar member 22 is secured to the metallic sleeve 6 adjacent the inner end of the resilient sleeve by any suitable means such as soldering. In addition, a portion of the flange 6 is screw-threaded as indicated at 24 so as to be engaged by a cap or nut member 26. This nut member 26 is in turn provided with an annular upwardly extending projection 28 which is adapted to engage the lower surface of a clamping ring or gasket 30. This clamping ring 30 is preferably of metal and is of such a thickness that it may be moved freely within the angular space between the casing opening I! and the flange member 6 in order to compress the resilient sleeve 20 against these two surfaces. v

The upper end pf the casing 2 is likewise provided with a slightly tapering cylindrical hole 32 through which the conductor l6 extends. .The casing preferably extends inwardly at this end to assume a dome-shape and provide sufllcient space within the bushing for expansion of the insulating fluid. The surface of the opening 32 is preferably left in a roughened condition for the same reasons set forth above.

A resilient sleeve 34 is disposed within the opening 32 to seal the space between the casing and the conductor and may b vulcanized or cemented to the opening at 33 if desired. A second metallic collar member 36 is secured to the conductor to engage the lower end of this sleeve while a cap 38 is secured to a threaded portion 40 of the conductor. This cap includes an annular flange 4| which extends beyond the top edge of casing 2 and has a downwardly extending annular portion 42. This portion 42 is adapted to engage a clamping ring 44 to cause it to compressthe resilient sleeve 34. Likewise a resilient gasket member 46 is disposed between the bottom of the cap 38 and the top of the casing 2 to prevent moisture from entering the opening.

A fish paper gasket 48 is cemented on the upper edge of the cap 38 and closely engages the threaded portion 40 of the conductor IE to prevent any moisture entering the opening through the threads. A lock nut 50 is threaded to the portion 40 of the conductor to maintain the device in assembled position and furnish a base against which an electrical conductor may be secured for connection with the apparatus within the casing.

It will appear that the resilient sleeves 20 and 34 will be compressed between their cooperating collars so as to completely seal the openings in which they are disposed. These collars, in addition, will prevent displacement of the sleeves even when they are not cemented to the opening, and it is within the scope of the invention to so dispense with the cementing or vulcanizing operation.

At the lower end of the bushing is an opening 52 for filling and draining the device of insulating fluid. This opening is adapted to be closed by means of a removable plug 54 which is shown more in detail in Fig. 3 of the drawing. As shown in this figure, a resilient sleeve 56 is disposed within the opening while a bolt designated as ii and having a conical portion 60 at its inner end in turn extends through the sleeve. The bolt 54 includes a head 62 which is larger than the inner diameter of the sleeve 56 yet smaller in diameter than the opening 52; Disposed between the inner surface of the sleeve 56 and the bolt, 58 is a split metallic sleeve designated at 54 which has a first conical surface 65 for engaging the surface of the bolt at 60 and a second conical surface 34 adapted to be engaged by an annular wedge 44 of triangular cross-section. This wedge 63 is movable axially along the bolt when a nut 10 is tightened thereon to extend the sleeve 64 and compress the resilient sleeve 56 against the roughened surface of the opening 52. The bolt 58 may be slotted at its outer end as shown at H to' facilitate holding it in place while tightening the nut 13. A lock nut 12 may be provided, if desired.

It will be evident that upon loosening the nut 10, the resilient sleeve 56 will come back to its also within the scope of the invention to dispense with these collars. In Fig. 4 is shown such a modiflcation in which cementing, vulcanizing or the like is relied upon entirely for maintaining the resilient sleeves in place. As shown in this flgure, a resilient sleeve 34' is secured to the conductor l6 as by cementing or vulcanizing at 14. The sleeve 34, in addition, engages a surface of the opening 32' at the end of the casing 2' and may be cemented thereto as shown at 16. A cap member 38 is secured to the threaded portion 40' of the conductor so as to compress a resilient gasket 46' between its lower surface and the upper end of the casing. A gasket 43 and lock nut 50' may be employed in a manner similar to the arrangement of Fig.

The lower end of the casi of the apparatus of Fig. 4 may be assembled in this same manner and the collar shown at 22 in Fig. 2 dispensed with.

From the foregoing it will appear that the present invention provides a novel and improved means for sealing the interior of an insulating bushing in such manner that the casing is not subjected to any dangerous stresses as a result of longitudinal movement between it and the conductor assembly. As the resilient sleeve itself is protected from moisture, these sealing properties will be maintained over a long period of time. 7

Since various modifications of the specific apparatus shown and described will appear to those skilled in the art, it is intended that the invention should be limited only by the appended claims interpreted in view of the prior art.

I claim as my invention:

1. In an insulating bushing, a tubular insulating casing defining an insulating chamber, and having an end portion extending inwardly to form a substantially circular opening, a rigid conducend of said conductor to compress said gasket against said casing, and an annular projection on said .capffcr fitting within the space between said conductor and'said casing to engage the outer end of said sleeve;

3; In a 'high tension 'insulatingibushing, a tubular insulating casing defining a central insulating ehain-bereand having an end portion extendg inwardl "toward the-axis thereof to form van g'ixial mu g, conductor; extending aid casing, a resilient sleeve g I pening aboutsaid conductor, a bular insulating casing definin v g g 'jsket-engaging'the outside of said caschamber and having an end portion extending a ing about said'g-opening,*a collar member secured inwardly to form a substantially circularf'cen "l5 tosaidconductorto engage the inner end of said tral opening, a. rigid conductor extending a idaily' 's1eevefand'1imit its;inwardmovementya cap" sethrough said casing, a. resilient sleeve disposed in said opening about said conductor and com pressed between it and the edge of said opening tor extending axially throughsaid'casing,a silient sleeve disposed in said openihgabouts conductor and compressedtherebetween f ductor to compress said; ins 2. In a high tension insulaft said gasket ainst said casing, and an annular member'f-forced: gainstlthe outer end 01' said to form a seal therebetween, a resilient gasket 2qi sieeve by ;said c ap to "compress the sleeve into engaging the outside of said casing about said sealing engagement with said casing and said opening, a collar member secured to said conducconductor. I

tor to engage the inner end oisaid sleeve and WILLIAM H. JACOBI. limit its inward movement, a cap secured to the ofisaid;conductorito compress 4 

